1. Field of the Invention
The invention relates to a laminate comprising a substrate that is wholly or partially non-electrical conducting and at least one layer of a polyamine polymer.
2. Description of the Prior Art
A laminate such as the above is known from U.S. Pat. No. 4,701,351 and serves as a substrate for printed circuits. To this end the laminate is provided with a metal, often copper or nickel. Such metallization can be carried out in an electroless metallization bath, in which a reaction takes place that is catalyzed by noble metal. The laminate known from U.S. Pat. No. 4,701,351 comprises a layer of polyamine polymer which serves to provide the surface area to be metallized with sufficient catalysts through complexing with noble metal ions.
There are several drawbacks to the laminate according to U.S. Pat. No. 4,701,351. Firstly, it can be seen that in some types of substrates metallization across the surface area has been uneven. A possible explanation for this is formed by slight dissolution of the polyamine polymer in the metallization bath. Secondly, this dissolution may be attended with the drawback of noble metal ions being released in the metallization bath. Such baths as a rule contain constituents like formaldehyde, which are capable of reducing noble metal ions to metallic noble metal. The presence of noble metal in a metallization bath will have a negative effect on the bath: the noble metal will start to act as a metallization seed of free noble metal, thus causing metal clumps to be formed.
From U.S. Pat. No. 4,701,351 a process is also known for the deposition of a noble metal onto an electrical non-conducting substrate or onto an electrical non-conducting section of a substrate, the noble metal being tightly bound to the substrate, which process comprises coating the substrate with a layer of polyamine polymer and contacting the coated substrate with noble metal ions.
The drawback to this process is that it is not possible to affect the polyamine polymer's complexing sites. This is of importance because there are various types of metallization baths requiring the utilization of different amounts of noble metal catalyst on the substrate. Thus, the use of a metallization bath requires the presence of just the right amount of noble metal catalyst properly distributed on the substrate. In particular, metallization at sites of too much noble metal concentration will be attended with blistering.
The above-mentioned drawbacks are obviated with the use of the laminate and process according to the invention.